Four different forms of mouse glutathione S-transferases were purified. F1, F2 and F3 transferases were purified from mouse liver by ammonium sulfate fractionations, DEAE-cellulose, CM-cellulose and hydroxyapatite chromatography. F transferase from mouse testis was partially purified from mouse testis by ammonium sulfate fractionations DEAE cellulose and hydroxyapatite chromatography and isoelectric focusing. Antisera were raised in rabbits against each form of transferase. The following biochemical parameters were determined for each mouse transferase: (a) native and subunit molecular weight; (b) Km for 1-chloro-2,4-dinitrobenzene and GSH; (c) isoelectric point; (d) Ki for S-(2,4-dinitrophenyl)glutathione; (e) immunological cross reactivity among different forms of transferase; (f) thermal stability and pH-dependent activity; (g) amino acid composition and peptide mapping for liver F1, F2 and F3 transferases.